Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$54.84	10.169%	$60.4167	$60.42	$60.40	$60.40
Purchase #2	$29.25	12.406%	$32.8788	$32.88	$32.90	$32.90
Purchase #3	$131.35	7.666%	$141.4193	$141.42	$141.40	$141.40
Purchase #4	$30.96	5.139%	$32.551	$32.55	$32.55	$32.60
Purchase #5	$101.42	12.334%	$113.9291	$113.93	$113.95	$113.90
Purchase #6	$16.37	13.508%	$18.5813	$18.58	$18.60	$18.60
Purchase #7	$46.65	3.469%	$48.2683	$48.27	$48.25	$48.30
7 purchase totals =	$410.84		$448.0445	$448.05	$448.05	$448.10